Electric furnace process



Jan. 4, 1938. G. E. SEIL 2,104,530

ELECTRIC FURNACE PROCESS Filed Nov. 28, 1936 H m II I FIG.

Q INVENTOR GILBERT 5.5511.

a mrm ATTORNEY.

patented Jana ti, iddd I fi th? Claims.

This invention revolves about smelting operations, such as the refiningof alloys and relates more particularly to term-alloys includingchromium.

i-lleretoiore, I have proposed for this purpose a process, the essenceof which is the production within a hollow electrode of a highlyoxidizing reagent for use subsequently in admixture in liquid phase witha bath of molten metal to be refined, by virtue of which the oxidizingreagent omdlizes in that hath oxidizrable impurities present therein,coupled with increments to the bath of desirable metal released from thereagent when it gives up its oxygen to the impurity.

This reagent is produced by supplying to the bore oi an energized hollowsubstantially horizontal electrode of an electric furnace having anatmosphere oi carbon monoxide, cores containing comminuted materialscapable of yielding under the influence of the heated zone of theelectrode,

molten metal having a metal oxide dispersed therein, detaining the corematerials in the heated zone long enough for the molten metal to attaina temperature substantially above its melting point, to increase thesolubility function of the metal for'the metal oxide.

When attempt was made to practice this process, disadvantages wereexperienced under certain conditions in uninterruptedly passing thecores into the bore of the electrode and through the heated zonethereof. So to overcome this is an object of this invention to the endthat the functioning of the furnace shall program smoothly anddependably. This object is attained by rotating the hollow electrodewhile the production oi the refining reagent proceeds therein.

a furnace with these advantages has been devised by me. It forms thesubject-matter of my patent application Ser. No. 22,963, filed May 23,1935. That case is drawn to describe a multiplicity of details of acomplete electric furnace including features of construction ofelectrode carriage, electrode cooling, core feeding mechanisin, and soon. That case has its emphasis directed to apparatus even though itdescribes a mechanism in which the process of this invention may becarried out. So this case has its emphasis directed toward the processirrespective of the specific apparatus that may be used in its carrylogout. Nevertheless, since everything disclosed in that case iscontemplated herein, the priority date of that case will be claimed forthis one, on the principle that this is a continuation-in-part of mysaid earlier application.

Rather than reuse, in reiteration, all of the (or. is-1c) many pages ofdescription and drawings of that case, only that portion thereof is usedherein- Which has direct reference to the novel process steps to beclaimed in this patent.

The invention hereof is diagrammatically il- 6 lustratedin theaccompanying drawing in which,

Figure 1 shows in skeleton form the essential parts and elements of anelectric furnace suitable for carrying out this invention. Such afurnace is shown in greater detail in my said copending l0 patentapplication Ser. No. 22,963.

Fig. 2 illustrates the novel effects attained by the rotation of thehollow electrodes showing particularly the behavior of the cores due tothat rotation; and

Fig. 3 is a transverse cross sectional View taken along the lines 3-3 inFig. 2.

In Fig. l of the drawing, ill and l 2 indicate substantially horizontalhollow energizable electrodes having adjacent ends it and itrespectively for supporting an arc therebetween of sufiicient intensityto heat the region of the arc ends of the electrodes to a. requisitetemperature. it indicates a bore of each electrode, and it any suitablemechanism for rotating the electrodes while en- 'ergized. Theelectrodes, of course, are to be housed in an operable electric furnacewith usual boundary walls and. top and provided with a hearth ll adaptedto hold a bath of molten metal material it having an oxidizable impurityto be refined therefrom and having on the bath a slag it containingoxide material. To the bores of the electrodes are forcibly suppliedcores 2!], and from the are ends of the electrodes there fall drops itof the refining reagent. The reagent 5 is highly oxidizing and includesa metal desirable in the refined metal to be recovered from the bathsaturated with a metal oxide dispersed or dissolved therein whose metalalso is desirable in the refined metal. The oxide is reduced to metal 40by the transference of the oxygen thereof to combine with the omdizableimpuritypf the bath (such as carbon). The impurity in the form of anoxide departs from the bath of metal being refined as a gas if gaseous,or into the slag if a solid. As the usual impurity is carbon, whenoxidized it formscarbon monoxide and this, in being continually evolved,forms the atmosphere of the furnace. The reduced metal forms an additionto the metal content of the bath.

The cores 20 are composed of comminuted materials comprising those thatare translatable under the conditions of temperature obtaining in theheated zone of the electrode, into a metal refining reagent. Moreparticularly those mc.- 55

terials can be a metal oxide preferably as an ore; a reducing agent suchas carbon in quantity insufficient to reduce all of the metal oxide sothat the end product of the reactions in the electrode will be reducedmetal and unreduced metal oxide; and a corrective for controlling thepassage of the reactive materials through the heated zone of theelectrode whereby the reduced metal yield ed therein is retained thereinlong enough to become superheated high enough above its melting point tobecome a solvent for the unreduced oxide but below the melting point ofthe oxide. A satisfactory degree of superheat is of the order of 600 'F.above the melting point of the metal. The result is the emission fromthe electrode of an oxidizing metal refining reagent. These reactionsand the manner of attaining these results form the subject-matter of mypatent application Ser. No. 59,690, filed January 18, 1936, (now PatentNo. 2,070,186) and of its predecessor patent applications referred totherein, on which it depends for priority.

As the metal oxide is reduced to metal which first appears in the formof drops thereof, the reduced metal occupies less volume than theconstituents which yield it. This causes the cores to become pitted orpossessed of pores. The outer surface sections of the cores disintegrateslowly.

under the influence of the heat, although they 'hold the metal in placelong enough to attain its desired superheat. As long as the cores are incore form, they exhibit a spon e-like function. Nevertheless, as thedrops of metal form, they should be kept away from the carbon of theelectrode and this is done to some extent by the sponge-like action ofthe core provided however,

the drop is not allowed to remain in too long contact with the carbon.Otherwise the metal will stick to the carbon and freeze the core againstfurther forward progress thereof through the bore of the electrode. Sucha prolonged contact of the core with one spot in the electrode tends tocause the oxide present in the core to give up some of its oxygen to thecarbon of the electrode. Again, as the metal oxide usually used in thisprocess is chromium oxide, or an ore containing it such as chromite, thereduced chromium being the heaviest constituent of the mass in theelectrode tends to settle out and stratify therein whereas it is highlydesirable to keep the molten or fiuid constituents in the electrode inwell dispersed or mingled condition. And further, if the reduced metalsuch as chromium should stick to the electrode, the carbon thereof beinghotter than the metal, will result in a detrimental pick up of carbon bythe metal.

For overcoming or at least discouraging the encountering of thesedisadvantages, it is proposed herein to rotate the hollow electrodes.Rotation I thereof results in an action illustrated in Figs. 2 and 3.Herein is illustrated what happens to the cores as they are forcedthrough the heated zone of the electrode so 20a represents a core 20 inone condition, 20b a core in a condition of partial disintegration, 200a core in an advanced state of disintegration, and so on. The bore ofthe electrode is shown in dotted lines in order to show the decreaseddiameter and conical shape assumed by cores during their advance throughthe heated zone as a result of the joint causes of the reduction of someof the metal oxide of the core to metal and of the rotation of theelectrode. The reaction between the reducing agent in the core and someof the metal oxide therein takes place under the influence Of theelectrode.

temperature encountered by the cores in the heated zone of the electrodewith the result that pores appear in the core and their size diminishes.Rotation of the electrode keeps the core and its contents free from thebore of the electrode because the core is caused to roll at a differentrate than the speed of the inner wall of the electrode because thediameter of the core is less than that of the bore. The steady wear onthe core and steady translation of its constituents discourages the corefrom breaking into fragments which would in turn cause jamming thereofin the bore. The space 22 existing be tween the core and the bore, thatincreases toward the arc end of the electrode, is useful andadvantageous because it provides a ready escape for the carbon monoxideof the furnace that is constantly produced due to the oxidation of thecarbon impurity of the metal being refined by the oxygen of theoxidizing refining reagent.

Satisfactory results have been attained by rotating the electrodes at aperipheral speed of three inches per minute, that is, one revolution ofa ten inch diameter electrode in ten and a half minutes.

Thus, the step of rotating the electrode serves the several purposes ofpreventing the reduced metal and its oxide from remaining in fixedrelationship with any particular spot in the bore of the electrode; ofmaintaining the fiuid constituents of the mass in the electrode inintermixed and intermingled condition; and of causing the cores todisintegrate gradually without breaking and thus avoid jamming thereofin the At the same time it assures the disintegration of the cores withthe translation of their reactant materials to progress uniformly,dependably and in an orderly manner.-

I claim:

1. The steps in a process of refining metal material comprising passinginto a substantially horizontal hollow electrode of an'electric furnacecores of a mixture capable of yielding metal and a metal oxide,meanwhile rotating the electrode.

2. The steps in a process of refining metal material comprising passinginto an energized substantially horizontal hollow electrode of anelectric furnace cores containing reactive materials capable of yieldingin the heated zone of the electrode a superheated molten metal having ametal oxide dispersed therein, meanwhile rotating the electrode.

3. The steps in a process of refining metal material comprisingsupplying to the bore of an energized substantially horizontal hollowelectrode of an electric furnace cores containing materials capable ofbeing translated under the influence of heat into molten metal having ametal oxide dispersed therein, detaining the core materials in theheated zone of the electrode long enough for the molten metal to attaina temperature substantially above its melting point, meanwhile rotatingthe electrode whereby the cores disintegrate gradually into conicalshapes as the core material thereof is translated.

4. The process of refining metal material comprising forming a moltenbath of metal having an oxidizable impurity therein and an oxidecontaining slag thereon; passing into an energized substantiallyhorizontal hollow electrode of an electric furnace cores containingmaterials capable of yielding in the heated zone of the electrode amolten metal having a metal oxide dispersed therein, meanwhile rotatingthe electrode, supplying the metal and oxide to the molten bath of metalin an atmosphere of carbon monoxide whereby there is effected anoxidation of the impurity of the bath with an increase of the metalcontent thereof and there is a departing of the resulting oxide from themolten metal, and then recovering the refined metal from the bath.

5. In the refining of a metal bearing material made up of a plurality ofconstituents including at least one metal as a desirable constituentthereof and at least one oxidizable undesirable constituent thereof, theprocess for modifying the proportion of certain constituents thereofwhich comprises forming a molten bath of the material to be refined andan oxidizing slag M thereon in a carbon monoxideatmosphere, forming anoxidizing reagent composed essentially of metallic oxide and a reducedmetal at a temperature in excess of the melting point oi the reducedmetal while conflned'in a substantially horizontal hollow electrode,meanwhile rotating the electrode, supplying a quantity of reagent to thebath for liquid admixture therewith under conditions for inducing anoxidizing action of the reagent upon the oxidizable undesirableconstituent of the molten bath by virtue of which the proportion thereofis decreased through conversion into an oxide, and then recoveringrefined metallic material from the bath.

GILBERT E. SEIL.

